1. Field of the Invention
The present invention relates to a ribbon cassette, more particularly, to a ribbon cassette and a printer that winds and transports an ink ribbon received in the ribbon cassette in a reliable manner.
2. Description of the Related Art
The known printer (line printer) having a long thermal head in which heat emitting elements are arranged along a width direction of printing paper has been used as a printing apparatus that rapidly performs a printing operation line-by-line or page-by-page on printing paper.
The printer uses a ribbon cassette in which a winding axis and a deliver axis winding the ink ribbon in both sides are separated to be rotatably disposed in the cassette case having a substantially rectangular shape. The ribbon cassette has a cassette case that forms a transport passage of an ink ribbon transported and supplied from a supplying axis to a winding axis between both axes. When the ribbon cassette is mounted, the thermal head of the printer is disposed between both axes. The thermal head is disposed such that the ink ribbon located in the transport passage is interposed therebetween, and the thermal head presses on and comes in contact with a platen so as to be ready to perform the printing operation.
Because a printer shows a tendency to decrease in size, it is necessary to decrease the size of the ribbon cassette mounted in the printer as well.
However, in the ribbon cassette, a space called a pancake receiving the ink ribbon wound between a pair of axes occupies most volume thereof. For this reason, the size of the cassette case increases, whereby it is difficult to reduce the size. Furthermore, it is difficult to reduce the size of the printer that receives the ribbon cassette as the size of the ribbon cassette decreases.
In order to decrease the size of the ribbon cassette, for example, the following ribbon cassette has been developed. The ribbon cassette includes a first receiving portion, a second receiving portion disposed at a predetermined interval from the first receiving portion, a cassette case having first and second connecting members connecting end portions of the first and second receiving portion, and a supplying axis and winding axis that are rotatably received in the supplying axis and the winding axis, respectively.
In the ribbon cassette, a first supporting portion formed of a wall portion that is bridged between the first and second connecting members is provided, and a second supporting portion is provided in the second receiving portion receiving the winding axis so as to correspond to the first supporting portion along the width direction of the ink ribbon. An example of the ribbon cassette is disclosed in JP-A-2001-205905.
In the ribbon cassette, the ink ribbon delivered from the winding axis is bent at the first supporting portion and the second supporting portion, whereby the ink ribbon is wound on the winding axis through the transport passage having a crank shape. When the ribbon cassette is mounted in the printer, the ribbon cassette is formed such that the thermal head of the printer is disposed between the first receiving portion and the wall portion, and a part of the printing-portion paper transport unit faces a space between the second receiving portion, which receives the winding axis and the wall portion. The ribbon cassette has been contrived to have a small size by reducing an unnecessary space in the cassette case. In the printer using this ribbon cassette, because the reduced space of the ribbon cassette can be effectively used, the printer may become small and thin.
In the printing-portion paper transport unit, a paper transport roller (which extends in the width direction of the ink ribbon and is rotatably supported), a driven roller (which extends in the width direction of the ink ribbon and is rotatably supported in contact with the paper transport roller), and a driven-roller mounting plate (which extends in the width direction of the ink ribbon and detachably supports the driven roller to the paper transport roller) are sequentially disposed in a height direction of the wall portion. When printing paper is interposed between the paper transport roller and the driven roller, the transport roller rotates such that the paper is supplied to a printing portion in which the thermal head is disposed or the paper is transported from the printing portion in the backward transporting direction of the transport.
However, the known paper transport roller or the driven roller is generally made of metal substances. Accordingly, while the printing paper is printed in the forward and backward direction respectively, the transported ink ribbon is drawn and wound on the paper transport roller or the driven roller due to static electricity charged to the ink ribbon, whereby the quality of printing image may be deteriorated or the ink ribbon may be cut.